Before Pharrell Williams’ song “Happy” was nominated for an Academy Award, before it reached the top of the Billboard charts, before it garnered 182 million views on YouTube and before it sold more than a million copies, it was just another song that wasn’t even getting played on the radio. Then, on Nov. 21, 2013, Pharrell released “Happy” with a music video and everything changed.

“Zero airplay, nothing. And the next thing you know, we put out the video on November 21 — all of a sudden, boom,” Pharrell says. “When I say, ‘Boom,’ I mean boom.”

People around the world responded to “Happy” by uploading videos of themselves dancing to the catchy song, from Malawi to Iceland to Washington, D.C. During Pharrell’s interview for “Oprah Prime,” Oprah plays a montage of these videos. As Pharrell watches, he becomes overwhelmed and begins to cry.

Oprah laughs, then offers an explanation for why Pharrell’s reaction is so emotional. “You know, it’s being used for something greater than yourself,” she says. “I get that.”

“It’s overwhelming because it’s like, I love what I do and I just appreciate the fact that people have believed in me for so long, that I could make it to this point, to feel that,” Pharrell says through tears.

“I get it,” Oprah says. “I so now get why it’s so infectious, because it came from such a clear space that the energy was absolutely uninterrupted by anything other than allowing it to flow from heart to heart. And that’s what happens when you see it.”